Drip irrigation tape and method of manufacture

ABSTRACT

A drip irrigation hose is formed from an elongated flat strip of flexible material. One side edge portion of the strip is deformed to form a series of indented channel formations deformed out of the plane of the strip, and the strip is then folded with the deformed side edge portion outermost and the channel formations facing inwardly and overlapping the underlying opposite side edge portion of the strip. The opposite side edge portions are sealed together to form a main conduit within the strip and a series of secondary conduits along the channel formations. Each channel formation has a series of spaced inlet channels extending transversely across the innermost side edge of the strip and into the secondary conduit.

CROSS-REFERENCES TO RELATED APPLICATIONS

This is a divisional of application Ser. No. 08/383,885, filed Feb. 6,1995, which was a C-I-P of application Ser. No. 08/194,854 filed Feb.14, 1994, now U.S. Pat. No. 3,387,307, which was a continuation ofapplication Ser. No. 08/015,080 filed Feb. 8, 1993 now U.S. Pat. No.5,318,657, which was a continuation of application Ser. No. 07/722,535filed Jun. 27, 1991 (abandoned), which was a divisional of applicationSer. No. 07/485,778 filed Feb. 22, 1990 (abandoned), which was acontinuation of application Ser. No. 07/332,588 filed Apr. 3, 1989(abandoned), which was a continuation-in-part of application Ser. No.07/156,413 filed Feb. 16, 1988 (abandoned).

U.S. Pat. No. 4,722,759 of Roberts et al. and U.S. Pat. No. 4,807,668 ofRoberts are related to this application.

BACKGROUND OF THE INVENTION

This invention relates generally to drip irrigation tape.

The drip irrigation system consists of lengths of plastic tubing or tapeplaced above ground or underground near the roots of plants, the tubinghaving numerous small outlets at spaced intervals supplying drops ofwater continuously to the plants. This allows the amount of watersupplied to be controlled more precisely, conserving water, improvingcrops and reducing salt accumulation and fertilizer loss in the soil.

In my previous U.S. Pat. Nos. 4,722,759 and 4,807,668, referred toabove, a drip irrigation tape is described in which a strip of flexiblematerial is formed with an indented groove extending lengthwise adjacentone side edge of the strip, the other side edge being folded over tooverlap the first side edge and form a first or main water conduit. Theoverlapping side edges are sealed together on opposite sides of thegroove to form a seam in which the groove defines a secondary conduit.Spaced inlets from the first conduit to the secondary conduit andoutlets from the secondary conduit are provided, so that fluid suppliedto the first conduit flows into the secondary conduit and from thereleaks slowly out of the outlets into the surrounding soil.

A method and apparatus for fabricating such tape was described in myprevious patents, which consisted of first forming the groove on avacuum drum, then folding the strip lengthwise before sealing theoverlapping edges at or close to the apposite sides of the groove bymeans of a heat sealing wheel.

In my previous patents the secondary conduit was formed by a straight,continuous or segmented channel. However, there is some advantage inproviding a non-straight path to create some turbulence in the fluidflowing along the channel or conduit. Thus, in U.S. Pat. No. 4,473,191of Chapin one of the embodiments shows a drip irrigation tape in whichthe flow restricting passage is in the form of a zig-zag or serpentinepath. In this case the passage is formed by depositing a flat ribbon ofplastic onto one side edge of the tape and then deforming the ribbon toform the serpentine path using a suitable molding wheel. One problemwith zig-zag flow restricting passages is that small particles of soilor dirt may become trapped in the confined space of the passage,blocking flow along the passage and thus reducing or stopping the flowof water into the soil.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an improved dripirrigation tape.

According to one aspect of the present invention a drip irrigation tapeis provided which comprises a strip of flexible material having a seriesof spaced, indented channel formations formed in one face of the stripalong a first side edge portion by molding the strip while hot, eachchannel formation including a first channel portion extending lengthwisealong the strip and a plurality of spaced, parallel inlet channelsextending transversely into the first channel portion. The strip isfolded lengthwise with the first side edge portion overlying a secondside edge portion to form a main conduit, and the first and second sideedge portions are sealed together at least along the opposite sides ofthe channel formations so that each channel formation defines asecondary conduit. The inlet channels connect the main conduit to thesecondary conduit and at least one outlet is provided to connect eachchannel formation to the exterior of the structure. Each formation maybe separated from the adjacent formations by means of transverse seallines.

The first and second side edge portions are preferably sealed togetherby spaced seal lines on opposite sides of the channel formations. Theseal lines joining the overlapping tape portions together may be spacedfrom the outer side edges of the channel formations so that if any dirtor sand blocks the serpentine portions, the back up pressure of waterbehind the blockage will force the overlapping, unconnected flat tapeportions on either side of the channel to deform outwardly, tending toshift or release the blockage. This has been found to reduce suchblockages substantially, leading to improved flow characteristics.

The overlapping side edge portions may be sealed together wherever theycontact one another, i.e. everywhere except the indented areas of thechannel formations, for example by means of heat sealing, ultrasonicwelding, or by means of a thin layer of adhesive covering the regions ofthe second side edge portion of the tape which will lie under theoverlapping first side edge portion. Alternatively, they may be sealedonly along spaced seal lines extending along opposite sides of thechannel formations. In the latter case, formation of the outermost sealline leaves a free flap along the outer edge of the second edge portion.It has been found that roots tend to grow along this flap between theflap and the underlying tape, leading to blockages of the outlets ifthey are formed by gaps in the seal line. The outlets thereforepreferably comprise slits or holes pierced in the outermost wall of thesecondary conduit. The strip is preferably folded with the second edgeportion on the inside.

The first channel portion may be straight and a second, serpentinechannel portion may extend from the first portion. Preferably, theinlets comprise parallel, indented inlet channels extending into thestraight inlet portion of the channel formation. The cross-sectionalarea of each inlet channel is much less than that of the straight inletportion. The serpentine portion also has a cross-sectional area lessthan that of the inlet portion. The inlet channels and larger, straightinlet portion act as a filter or screen to reduce the risk of debrisblocking flow. Preferably, spaced inlet channels are provided along theentire length of the larger, inlet portion. Any one of the inletchannels can feed the secondary conduit, significantly reducing the riskof any plugging and blocking of flow in the secondary conduit.

In one embodiment of the invention, the straight inlet portion andserpentine portion are aligned and extend lengthwise along the firstside edge portion. In an alternative embodiment, the channel formationincludes at least one U-bend in which the channel direction is reversed,so that adjacent channel sections on opposite sides of the bend extendgenerally parallel to one another and the first side edge of the tape,but in opposite directions. Preferably, two U-bends or reverses indirection are provided. This allows the secondary conduit to be mademuch longer for the same drip outlet spacing, and thus allows thechannel size to be made larger for the same drip rate.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be better understood from the followingdetailed description of some preferred embodiments of the invention,taken in conjunction with the accompanying drawings, in which likereference numerals refer to like parts, and in which:

FIG. 1 is a top plan view of a portion of a drip irrigation tapeaccording to a first embodiment of the invention;

FIG. 2 is an enlarged sectional view taken on line 2--2 of FIG. 1;

FIG. 3 is a sectional view taken on line 3--3 of FIG. 2;

FIG. 4 is a sectional view taken on line 4--4 of FIG. 2;

FIG. 5 is a sectional view taken on line 5--5 of FIG. 2;

FIG. 6 is a sectional view taken on line 6--6 of FIG. 2;

FIG. 7 is a top plan view of a portion of hose showing an alternativeserpentine channel;

FIG. 8 is a similar top plan view showing a further type of serpentinechannel;

FIG. 9 is a top plan view of a portion of a drip irrigation tapeaccording to a second embodiment of the invention;

FIG. 10 is an enlarged view of part of the serpentine portion of thesecondary conduit of FIG. 9;

FIG. 11 is a section on the lines 11--11 of FIG. 10;

FIG. 12 is a sectional view on the lines 12--12 of FIG. 11;

FIG. 13 is a section similar to FIG. 12 illustrating an alternativemethod of joining the side edge portions of the tape;

FIG. 14 is a top plan view of a portion of a drip irrigation tapeaccording to a third embodiment of the invention; and

FIG. 15 is an enlarged top plan view showing a modified serpentineconfiguration.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIGS. 1-6 of the drawings show a drip irrigation tape or hose 10according to a preferred embodiment of the present invention. The tape10 is formed from a strip of flexible, water impervious material such asmedium or high density polyethylene, or other suitable polyolefin,suitably dimensioned for folding over with its side edges overlapping toform a primary conduit 12 for water or other fluid. A series of spaced,indented grooves or channel formations 16 are formed along one side edge17 of the strip. The opposing side edges 17,19 are sealed together alongspaced seal lines 18,20 which are spaced from the outer side edges 22 ofthe groove, as best seen in FIG. 1.

In the embodiment shown in FIG. 1, each channel formation includes astraight, inlet portion 23 and a serpentine portion 24 of a desiredlength extending along the tape. Each inlet portion 23 has a pluralityof spaced, parallel inlet channels 26 extending transversely intoportion 23, and a series of parallel outlet channels 28 are provided atthe opposite end of the channel formation. Inclined transverse seallines 30 separate the successive channel or groove segments 24. Theinlet and outlet channels are formed by suitable indentations in theoverlapping side edge of the strip, in the same way as the serpentinegroove. Gaps 32,34 are provided in the seal lines 18,20, respectively inthe region of inlets 26 and outlets 28, as seen in FIG. 1. The inletchannels will extend over the underlying side edge 19 of the tape, asillustrated in FIG. 5, to provide the necessary inlet opening fromconduit 12.

Although separate serpentine channel segments are shown in FIG. 1, thegroove or secondary conduit may alternatively be continuous, with spacedinlets and outlets provided along its length in an equivalent fashion.Instead of a plurality of parallel inlets and outlets as shown in FIG.1, pairs of inlet channels defining a V-shape leading into the conduitmay be provided, as in my U.S. Pat. No. 4,722,759 referred to above, andthe outlets may be defined simply by spaced breaks in one of the seallines. Alternatively, a single outlet may be provided in place ofparallel outlets 28.

FIGS. 7 and 8 show two alternative configurations 33,35 for theserpentine portion 24 of the channel. The configuration will depend onthe desired flow characteristics and also in ease of manufacture of thechannel or groove. The turbulent flow resulting from the constantlychanging direction will tend to keep small particles of grit and dirtmoving along the channel without causing a blockage. The provision oflinear seal lines spaced from the side edges of the channel has theadvantage of being simple to manufacture and also of helping to shiftany blockages. Thus, if the serpentine channel 16 of FIG. 1 shouldbecome blocked, for example at the location shown in FIG. 6, water willback up behind the blockage as it is flowing constantly along the mainconduit and into the secondary conduit. The resultant water pressurewill cause the opposing faces 25 of the side edges of the strip onopposite sides of the channel between the seal lines to deform away fromone another, as generally indicated in FIG. 17. This allows a gush ofwater to flow along the channel, tending to shift the blockage. Afterthe blockage has shifted, the overlapping side edges will collapse backtogether as shown in FIG. 6. The design of the serpentine channel withspaced seal lines thus considerably reduces the risk of blockages whichwould otherwise cut off water from adjacent areas of soil surroundingthe tube.

By providing a large number of inlet channels all connected to astraight inlet channel portion 23 of relatively large cross-section, therisk of blockage at an inlet stopping flow through any secondary conduitsegment is also reduced considerably. As long as one inlet channelremains unblocked, fluid will be supplied to the secondary conduit. Anydebris small enough to enter the inlet portion 23 via an inlet channelwill be too small to cause a blockage.

The drip irrigation tape of FIGS. 1-6 is preferably made in the mannerdescribed in my U.S. Pat. No. 5,375,770, the contents of which areincorporated herein by reference. A strip of polyethylene material isfirst extruded from an extruder and the channel formation is then formedin the first side edge portion of the strip by passing it between ashaping drum and an opposing guide drum. The shaping drum will have aseries of indented channels each corresponding in shape to the shape ofthe desired channel formation. The indented channels are connected to avacuum source so that the molten strip material passing over the channelwill be pulled into the channel and shaped. A folding mechanism islocated downstream of the shaping drum for folding the strip with itsopposite side edges overlapping, followed by a heat sealing station forforming the seal lines to seal the overlapping edges together to formthe separate main conduit and secondary conduit segments. After the heatsealing station, the formed tape is passed over a series of guiderollers and cooling wheels before being wound onto a storage spool.

FIGS. 9-12 illustrate a drip irrigation tape or hose 50 according to asecond embodiment of the invention. The tape is formed from a strip offlexible, water-impervious material such as medium to high densitypolyethylene or other polyolefins, in the same manner as described abovein connection with the first embodiment. A series of spaced, indentedchannel formations 52, one of which can be seen in FIG. 9, are formed inone side edge portion of the strip adjacent one side edge 54. The stripis then folded so that the first side edge portion overlaps a secondside edge 56 of the strip to form a primary conduit and a series ofsecondary conduit segments.

Each channel formation 52 includes a straight, inlet portion 58connected to a serpentine portion. The straight portion 58 extends in afirst direction parallel to the side edge 54 of the strip, while theserpentine portion includes a first portion 62 extending in the oppositedirection to the inlet portion 58, a U-bend 64, and a second portion 65extending back in the opposite direction to portion 62. An outletchamber 66 of enlarged dimensions is provided at the end of serpentineportion 65, and an outlet slit 68 is stamped or cut in the upper wall ofchamber 66, as best illustrated in FIGS. 9 and 11. Thus, the channelformation 52 forming each secondary channel segment zig-zags or windsback and forth to extend the effective length of the secondary conduitwhile maintaining the same outlet spacing.

The channel formation 52 also includes a series of straight, parallelinlet channels 70 extending transversely into the straight, inletportion 58 at spaced intervals along the entire length of portion 58, asillustrated in FIG. 9. The overlap between the opposite side edgeportions of the strip is arranged such that the second side edge 56lying beneath channel formation 52 will be positioned beneath the inletchannels 70, as illustrated in FIGS. 9 and 12, leaving a gap 71 at theend of each channel 70 communicating with the main conduit for flow fromthe main conduit into channel 70. The straight inlet portion 58 has afirst end 72 and a second end 74, and the first portion 62 of theserpentine portion extends alongside portion 58 from the second end backtowards the first end. The inlet portion 58 is connected to the firstserpentine channel by means of a series of spaced connecting channels 75extending from the inlet portion across to the first serpentine portion62 adjacent the second end 74 of the straight, inlet portion, asillustrated in FIG. 9. Four connecting channels 75 are illustrated, butany number of connecting channels from one to seven or more may beprovided.

The outlet spacing of the hose is fixed, depending on the irrigationrequirements. This arrangement allows a large number of spaced inlets tobe used without reducing the length of the serpentine or flow reducingportion of the secondary conduit.

The shape of the serpentine portions of the channel formation isillustrated in more detail in FIG. 10. The serpentine shape comprises aseries of elongate chambers 76 offset alternately on opposite sides ofthe center line 77 of the serpentine section and interconnected byorifices 78 between adjacent ends of each pair of chambers. Flow will bein the direction of the arrow 79 in FIG. 10. Each chamber includes agenerally straight inlet end 80 forming a continuation of the orifice78, and a rounded outlet end 82 for producing a swirling, circular orvortex type of flow pattern in the water at the outlet end of thechamber. This will tend to reduce the flow rate, and will tend toproduce a little more turbulence in the transition from the outlet endof one chamber to the straight inlet end of the next chamber than acorresponding chamber shape in which both ends are rounded, as wasdescribed in my U.S. Pat. No. 5,375,770 referred to above. This isbecause the rounded ends can be more rounded, and the offset between thechambers is greater than in the previous configuration. The orificewidth is approximately equal to the width of the chambers.

As noted above, the first serpentine portion 62 extends back alongsideinlet channel 58 up to the first end of the inlet portion 58. Thechannel then changes direction around a U-bend portion 64 which connectsthe first serpentine portion 62 to second serpentine portion 65, whichextends back alongside portion 62 in the opposite direction, up tooutlet chamber 66. The second serpentine portion is of shape identicalto that of the first portion with respect to the flow direction of waterthrough the channel.

The first and second side edge portions of the tape or strip arepreferably secured together by means of spaced seal lines, asillustrated in FIG. 1. First and second spaced, parallel seal lines84,85 extend on opposite sides of the channel formation, with gaps 86 inseal line 85 to accommodate each of the inlet channels 70. The seallines 84 and 85 are connected together by spaced transverse seal lines87 between each pair of channel formations. Additional seal lines 88,89are provided between the straight inlet portion 58 and the firstserpentine portion 62, and between the two serpentine portions 62 and62, respectively, to prevent fluid flowing along the channel portionsfrom forcing the overlying portions of the strip apart and leakingacross the space between the adjacent channel portions. Seal line 88 hasgaps 90 to accommodate each of the connecting channels 75. Seal line 89extends from a location close to bend 64 up to the next transverse sealline 67. This arrangement seals off each portion of the secondaryconduit from the next adjacent portion, and seals straight inlet channelportion 58 from the interior of the hose except for via the inletchannels 70. In an alternative embodiment, some of the seal lineportions between inlet channels 70 may be omitted, for example alternateseal line portions between inlet channels 70 may be omitted.

The secondary channel formation 52 as illustrated in FIGS. 9-12 has theadvantage that the dimensions of both the inlet channels and theserpentine channel portions can be made larger than in conventionalsecondary conduits while maintaining the same flow rate. The spacingbetween the outlets 68 of successive channel configurations 52 will bedependent on the irrigation requirements, and in practice tape 50 willbe made with outlet spacings of 4", 8", 12" and multiples thereof. Theserpentine or tortuous portion of the secondary conduit is made longerthan the outlet spacing by winding it back and forth in a zig-zag ordoubled back pattern having at least one U-bend 64. With thisarrangement, the straight inlet channel portion is preferablyapproximately 1.25 to 1.50 times wider than the rest of the channels.The inlet channels 70 may be of width approximately the same as theserpentine channel portions to 20% less than the width of the serpentinechannel portions. The serpentine channel preferably has a width of0.030-0.100", and all of the channel portions preferably haveapproximately the same depth, in the range 0.015-0.035" deep. Thechannel width and depth may be designed for the desired flow rate, withthe channel being made shallower in depth as it is widened, in order tomaintain a desired flow rate. Generally, a wider channel is better as itpermits more deflection of the channel wall for pressure compensation.The depth of outlet channel 66 may be the same as or slightly greaterthan that of the remainder of the channel formation.

The multiple inlet channels 70 to a larger inlet portion 58 have ascreen effect to remove debris from the water entering inlet portion 58.Any debris small enough to enter portion 58 will be too small to causeany blockage of channel portion 58 or serpentine portions 62,65, whichare of a width equal to or greater than that of channels 70. As long asat least one inlet channel 70 is unblocked, this will be sufficient tofeed the secondary conduit and provide the desired drip rate at outletslit 68. The provision of four connecting channels 75 from the straightinlet portion 58 to the serpentine portion 62 further reduces the riskof any blockage stopping flow along the secondary conduit. Channels 75will be of approximately the same dimensions as inlet channels 70. Ifany one, two or three of channels 75 should become blocked, theremaining channels or channel will still provide a sufficient supply tothe serpentine flow portions of the conduit.

Although the width of the serpentine channel portions is relativelylarge, the winding nature of the path, along with the rounded ends ofchambers 76 introducing some turbulence in the flow pattern, will tendto reduce the flow rate so that the same drip rate is produced as for acorresponding straight conduit of smaller dimensions. The turbulent flowconditions will also tend to dislodge any small debris which manages toflow into the serpentine portions. The arrangement allows multiplespaced inlets to be used Without reducing the length of the serpentineor turbulent flow portion of the secondary conduit, unlike priorarrangements.

The tape or hose 50 of FIGS. 9-12 is preferably also formed by basicallythe same method as described in my U.S. Pat. No. 5,246,171 referred toabove, with appropriate modification of the shaping drum channels tocorrespond to the shape of channel configuration 52 of FIG. 9, andmodification of the heat sealing drum to provide ribs for forming theheat seal lines 85,86,87,88 and 89. Outlet slit 68 may be laser cut.Alternatively, the strip may be passed under a roller with a retractableblade which is suitably timed for punching successive slit outlets 68 inthe strip.

FIG. 13 illustrates an alternative method for making tape with thesecondary conduit configuration of FIGS. 9-12, or that of FIGS. 1-8. Inthis method, the various seal lines are eliminated and the overlappingside edge portions of the strip are secured together via a thin layer 91of adhesive laid down on the flat side edge portion of the strip. Theconduit configuration 52 may be vacuum formed on a shaping drum in asimilar manner to that described above. While maintaining the stripmaterial in a super-heated state, a film or layer 91 of adhesive is laiddown so that it completely covers the regions of the flat side edgeportion which will underlie the channel configuration in the oppositeside edge portion. In other words, the width of layer 91 will be greaterthan that of the channel configuration 52. The film layer will be very,thin, of the order of only 0.75 mil. thick. After the adhesive film islaid down, the opposite side edge is folded over in the direction of thearrow in FIG. 13, and pushed down over the strip so that the two sideedges are adhesively sealed together. With this arrangement, all regionsof the overlapping side edge portions outside the indented channelformation will be sealed together.

FIG. 14 illustrates an alternative, indented channel configuration 92for forming the secondary conduit which is 15 similar to that of FIGS.9-12 except that the straight inlet portion 58 is eliminated. Theconfiguration 92 is preferably formed by the same method as in theprevious embodiment, and has a first serpentine portion 93 having aplurality of spaced, parallel inlets 94 and extending in a firstdirection from inlets 94 up to U-bend 95. A second serpentine portion 96extends from U-bend 95 in the opposite direction to the first portion 93back past the inlets to an outlet chamber 97 having a slit outlet 98 asin the previous embodiment. The shape of the serpentine portions 93 and96 is substantially the same as that of the previous embodiment, andincludes offset chambers on opposite sides of the center line of theserpentine channel, each chamber having an inlet end with a flat endwall and an outlet end with a rounded end wall for introducingturbulence into the water flowing along the channel. Water will bedirected in a circular path around the rounded end wall in the oppositedirection to water flowing along the chamber, producing turbulence andretarding flow. This will tend to reduce the flow rate and allows thecross-section of the channel to be larger than that for an equivalentstraight channel for the same flow rate.

Spaced parallel seal lines 100,102,104 are provided between the firstserpentine portion 93 and the inlet ends of inlet channels 94, betweenthe two serpentine portions 93 and 96, and between the second serpentineportion and the outer side edge 54 of the strip. Transverse seal lines106 extend between the outermost seal lines in the space between eachadjacent pair of channel configurations 92. One or two of the seal lineportions between inlets 94 may be omitted in alternative arrangements.This will permit some expansion to clear blockages.

As in the previous embodiments, the width of each inlet channel isapproximately equal to that of the serpentine channel portions, reducingthe risk of blockage at the inlets. The irrigation hose as illustratedin FIG. 14 may also alternatively be made by the method illustrated inFIG. 13, eliminating the need for seal lines 100,102,104 and 106.

In the embodiment of FIG. 9-12 or that of FIG. 14, the dimensions of theserpentine channel portions may be as follows. The width of the straightportion of each chamber may be in the range of 0.030" to 0.100", whilethe width of each orifice connecting the adjacent chamber ends is about0.050". The radius of the rounded end wall is in the range from 0.020"to 0.040". The length of each chamber from the center of the inletorifice to the center of the outlet orifice is around 0.135". Thisarrangement will introduce sufficient turbulence to slow down the rateof flow through the serpentine portions and produce a desired outletdrip rate.

FIG. 15 is an enlarged view similar to FIG. 10 illustrated a modifiedconfiguration for the serpentine portions in either FIG. 9 or FIG. 14.In this version, the offset between the chambers 176 on opposite sidesof center line 177 is increased, and the connecting orifices 178 arenarrower in width than chambers 176. As in the previous embodiment,chambers 176 have a flat inlet end wall 180 and rounded outlet end 182.

Although some preferred embodiments of the invention have been describedabove by way of example only, it will be understood by those skilled inthe field that modifications may be made to the disclosed embodimentswithout departing from the scope of the invention, which is defined bythe appended claims.

I claim:
 1. A method of supplying water from a water supply at apredetermined drip rate from a plurality of spaced outlets along thelength of a drip irrigation hose, comprising the steps of:connecting oneend of a drip irrigation hose to a water supply, the hose being formedfrom a flat strip of flexible material having a series of spacedindented channel formations along one side edge portion which is foldedwith said one side edge outermost and overlapping the opposite side edgeportion to form a main conduit within the folded strip and a secondaryconduit along each channel formation which has inlets connecting themain conduit to each secondary conduit and at least one outletconnecting each secondary conduits to the exterior of the hose;supplying water at a predetermined flow rate along the main conduit;directing water from said main conduit into each of said secondaryconduits through a plurality of spaced inlets defining a firstpredetermined flow width in said one side edge connecting the mainconduit to each secondary conduit; directing water in a tortuous pathalong at least a portion of each secondary conduit which is ofserpentine shape at a flow rate which is reduced relative to the flowrate through the remainder of the conduit and at a second predeterminedflow width, said first flow width being in the range from 20% less thanthe second flow width up to a flow width equal to said second flowwidth; directing water out through at least one outlet connecting thesecondary conduit to the exterior of the hose; and directing water ineach secondary conduit to flow in a first direction along the length ofthe hose and then directing water to flow back in a second directionopposite to said first direction before directing water out of saidoutlet.
 2. The method as claimed in claim 1, wherein the step ofdirecting water out of said outlet comprises directing water through aslit in an outer wall of said secondary conduit.
 3. The method asclaimed in claim 1, including the step of directing water in eachsecondary conduit to flow in a third direction opposite to said seconddirection before directing water out of said outlet.
 4. The method asclaimed in claim 1, wherein the first flow width is in the range from0.020" to 0.050".